<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    var str = '123.45'

    // console.log( parseInt(str) ) //  123
    // console.log( typeof parseInt(str) ) // number

    // console.log( parseFloat(str) ) // 123.456
    // console.log( typeof parseFloat(str) ) // number

    // console.log( typeof Number(str) )


    // 隐式转换
    // console.log( typeof(str - 0) )
  </script>
</body>
</html>